NAME    [Toc]    [Back]

       adjtime - Correct the time to allow synchronization of the
       system clock

SYNOPSIS    [Toc]    [Back]

       #include <sys/time.h>

       int adjtime(
               struct timeval *delta,
               struct timeval *old_delta );

PARAMETERS    [Toc]    [Back]

       Points to the amount of time to be altered.  Points to the
       number  of  nanoseconds still to be corrected from an earlier
 call.

DESCRIPTION    [Toc]    [Back]

       The adjtime() function makes small adjustments to the system
 time (as returned by the gettimer() function), advancing
 or decreasing it by the time specified  by  the  delta
       parameter  of the timeval structure. If delta is negative,
       the clock is slowed down by incrementing  it  more  slowly
       than  normal until the correction is complete. If delta is
       positive, a larger increment than normal is used until the
       correction is complete.

       The  skew  used  to  perform the correction is generally a
       fraction of one percent. Thus, the time is always a  monotonically
 increasing function.

       A  time  correction  from an earlier call to adjtime() may
       not be finished when adjtime() is called  again.  In  this
       case,  the  delta  remaining  from  the  original  call is
       replaced  by  the  delta  of  the  current  call.  If  the
       old_delta  parameter  is  nonzero, then when the adjtime()
       function returns, the structure pointed  to  will  contain
       the time remaining from the earlier call.

       This call may be used by time servers that synchronize the
       clocks of computers in a local  area  network.  Such  time
       servers  would  slow  down the clocks of some machines and
       speed up the clocks of others to bring them to the average
       network  time.  The  adjtime()  function  is restricted to
       users with the superuser privilege.

NOTES    [Toc]    [Back]

       In BSD, system time is defined in  units  of  seconds  and
       microseconds,  while  in  POSIX  real time extensions, the
       units are seconds and nanoseconds.  However, the adjtime()
       function is not specified by POSIX.  Therefore, the existing
 BSD interface is preserved.

RETURN VALUES    [Toc]    [Back]

       On successful completion, the adjtime() function returns 0
       (zero). If the adjtime() function fails, it returns -1 and
       sets errno to indicate the error.

ERRORS    [Toc]    [Back]

       If the adjtime() function fails, errno may be set  to  one
       of  the  following  values: An argument address referenced
       invalid memory.  The process's effective user ID does  not
       have appropriate system privilege.

SEE ALSO    [Toc]    [Back]

       Functions: gettimeofday(2), gettimer(3)



                                                       adjtime(2)